It is common practice for therapists, physicians, athletes, and other individuals to utilize various electrostimulation treatment and therapy devices to promote muscle training, conditioning, and growth. In addition, devices often referred to as Transcutaneous Nerve Stimulation (“TENS”) units are employed to manage pain and discomfort by blocking the nerve signals from the area of discomfort to the brain. With muscle stimulation and nerve stimulation, a device is programmed to output various levels of electrical pulses. The frequency, duration, pulse width, and intensity of the output signal control the directed treatment goals.
With regard to muscle stimulation, there are a myriad of uses for these electrostimulation devices. Treatment categories can generally be divided between fitness, aesthetic, sport, pain management, rehabilitation, and vascular. Each is directed to a different stimulation goal. With fitness, the goal is generally to restore, improve, or maintain a good physical condition by building muscle, muscle tone, volume, trophism, metabolism, and the like. With aesthetic goals, the stimulator is often utilized on muscles in order to shape, firm, increase elasticity, refine, and increase caloric expenditure. Sports-minded individuals may use the device to increase muscular endurance and strength, increase blood flow to promote active recovery, and the like. When focus is on rehabilitation, muscular stimulation is needed to restore or otherwise redevelop a convalescent muscle. Under the vascular category of treatment programs, the goal is to improve blood circulation in the stimulated area to minimize circulatory problems, fatigue, lack of oxygenation, swelling, and other related problems. In pain management applications, electrostimulation devices are used primarily to alleviate muscle pain or other discomfort.
Regardless of the unique goal-dependent outputs of the device, electrostimulation works under a principle of muscle contraction. When an individual voluntarily contracts a muscle, the brain sends the information to the muscle via the motor nerve. With electrostimulation, a suitable electric current acts directly on the nerve by means of electrical impulses that reproduce the natural physiological phenomenon. These electrical impulses are applied to the user through attached electrodes. The electrodes are typically adhesively attached to the person or person's clothing. With electrostimulation a patient or user can achieve intensive muscular work without mental or cardiac fatigue, thus reducing joint and tendon constraints.
While electrostimulation can be used for the above-described purposes, the U.S. Food & Drug Administration (FDA) currently limits or proscribes the use of electrostimulation devices on certain areas of the body, including the pectoralis major (frontal chest/shoulder area) and latissimus dorsi (upper back area) muscle groups, because of the risk of inducing cardiac fibrillation in the event of device malfunction, misuse, or failure. Conventional electrostimulation devices are not capable of providing a level of self-monitoring and protection to permit the safe use of such devices in the cardiac region.
For example, U.S. Pat. No. 4,088,141 to Niemi discloses a fault circuit for a stimulator. The circuit may be incorporated into a medical transcutaneous nerve or muscle stimulator for disabling the output from the stimulator to stimulation electrodes connected thereto upon the occurrence of an undesirable output event of the kind that may result in an electrical shock or burn to a user of the stimulator. See also U.S. Pat. No. 4,068,669 to Niemi.
In U.S. Pat. No. 4,363,324 to Kusserow, a current stimulation apparatus includes a safety circuit. A safety circuit that disconnects the patient output from the operating voltage is employed as the protection installation and also responds when the patient current deviates from a pre-selected desired value adjusted on an intensity adjustment member.
U.S. Pat. No. 4,582,063 to Mickiewicz discloses a transcutaneous nerve stimulation device with sentinel. The device produces a sentinel pulse of known characteristics and an output response is measured. A sentinel warning signal is produced if an undesired output response is measured to alert the user to a potentially hazardous condition.
U.S. Pat. No. 4,706,674 to Dieken discloses an electrical stimulator utilizing an output current monitor. One embodiment of Dieken includes an additional current monitor, wherein a comparator is used to compare currents measured by both current monitors.
EP0367338 to Beun discloses an electrotherapy apparatus. EP0367338 discusses monitoring a sum of two currents to prevent a total output current exceeding a predetermined limit value.
U.S. Pat. No. 5,800,458 to Wingrove, commonly assigned with the present application, is directed to a compliance monitor for monitoring applied electrical stimulation. The compliance monitor comprises a current sensing element, a controller, and a timer. When the current sensing element senses that current is supplied through an output channel, the current sensing element outputs a signal to the controller.
Other documents that generally disclose and discuss various safety and protection schemes and the general state of the art include U.S. Pat. No. 4,769,881 to Pedigo et al., U.S. Pat. Nos. 5,081,989 and 5,092,329 to Graupe et al., U.S. Pat. No. 6,564,103 to Fischer et al., EP 0706806 to Cywinski, WO 82/00414 to Heath, PCT/US81/01055, DE 4029175, and DE 3216911.
While these safety systems can be effective in generally preventing delivery of excessive stimulation pulses, the systems are not specifically designed to prevent delivery of stimulation pulses that could induce cardiac fibrillation. Further, the current systems are not designed for the robust level of safety required to overcome the existing FDA proscription of use of electrostimulation devices on regions of the body where stimulation pulses might inadvertently induce cardiac fibrillation.
The need therefore remains for an electrostimulation device having a protection system that monitors and supervises treatment sessions, providing an elevated level of safety for users.